Activator solution rejuvenation



United States Patent 3,379,528 ACTIVATOR SOLUTION REJUVENATION RichardW. Henn and Nancy H. King, Rochester, N.Y., assignors to Eastman KodakCompany, Rochester, N.Y., a corporation of New Jersey No Drawing. FiledJuly 17, 1964, Ser. No. 383,517 4 Claims. (Cl. 96-28) This inventionconcerns activators for use with the photographic process known as thecolloid transfer process.

In the colloid transfer process, an image in soft adhesive organiccolloid is formed photographically and a discrete stratum of the imageis transferred to a receiving sheet to provide a reproduction of thesubject. The process is described in the Yutzy et a1. U.S. Patents2,596,756, granted May 3, 1952 and 2,716,059, granted Aug. 23, 1955, andembodies the exposure to a subject of a substantially unhardenedgelatino silver halide emulsion layer which may contain a gelatintanning silver halide developing agent as well as a non-tanning silverhalide developing agent. These patents are incorporated herein byreference.

Upon activation of the exposed gelatin emulsion with the alkalinesolution in the presence of the developing agent or agents, tanningdevelopment of the most exposed regions of the emulsion corresponding tothe highlights of the subject proceeds, although some development of theless exposed regions also takes place to provide visual density for thetransferred image, as explained in more detail in U.S. Patent 2,716,059.Thereafter, the developed emulsion is placed into contact with anabsorbent receiving sheet such as paper to cause the less exposedregions, and thus the less developed regions, of the emulsion to adhereto the receiving sheet. Subsequently, when the emulsion on the matrixsheet and receiving sheet are separated, a stratum of the less exposedregions of the emulsion remains on the receiving sheet and appears as apositive silver image of the original subject.

The colloid transfer process has been used extensively for officecopying purposes and it has been desirable to provide activatorsolutions for processing the exposed silver halide emulsion. Variousactivator solutions have been disclosed in the following U.S. patents:Yackel, 2,596,754; Yutzy et 211., 2,596,756; Yutzy et al,, 2,725,298;Yutzy et al., 2,739,890; Clark et al., 2,763,553; Cowden et 211.,2,835,575; Kendall, 2,852,371; Chain et al., 2865,745, etc.

In addition, the following U.S. patent applications also discloseactivator solutions for use in the colloid transfer process: Fruchard etal., U.S. Ser. No. 242,526, filed Sept. 5, 1962; Cowden, U.S. Ser. No.310,897, filed Sept. 23, 1963, and Yost, U.S. Ser. No. 227,562, filedOct. 1, 1962.

Colloid transfer activator baths, in general, are alkaline solutionswhich serve to activate the developer contained in the silver halideemulsion. However, various improvements over the basic alkaline solutionhave been made. For instance, certain activator solutions desensitizethe emulsion for roomlight handling, reduce the tendency for salts tocrystallize out of the solution, incorporate gelatin hardeners, improvethe temperature latitude, and the like.

All activator solutions have reduced usefulness following the activationof a number of matrices containing the silver halide emulsion and it hasbeen desirable to find a method of replenishing the activator solutionswith a universal replenisher which would essentially restore thesolution to Working strength without the necessity of discarding thecomplete solution and replacing with fresh activator. Therefore, it hasbeen desirable to find a replenisher which would preserve the particularcharacteristics of the activator solution, for example, temperaturelatitude, gelatin softening, or the like, but which would permitsatisfactory use of the activator for a larger number of matrices thanhas customarily been possible. It has also been desirable to provideease of replenishing the activator so that after a certain number ofmatrices have been processed, a predetermined amount of replenisher isadded.

We have discovered a method of replenishing used activator solutionusing lithium hydroxide coated matrix sheets or coated sheets which canbe packaged in a predetermined manner with the sensitive matrix sheets.

One object of this invention is to provide a method of replenishing aused or depleted activator solution. Another object is to provide aprocess of packaging colloid transfer matrices with a replenishing agentfor the activator solution. An additional object is to provideinterleaving sheets which can be used to repmlenish an alkalineactivator solution which would raise the pH to that found in the freshactivator solution. Additional objects will be apparent from thefollowing specification.

Lithium hydroxide is used as the alkaline material as an alkali which iscompatible with all activator solutions. A partcularly useful form ofthe lithium hydroxide is as its monohydrate. Sutlicient lithiumhydroxide is added to restore the activator to about its original pH. Ina useful embodiment, the lithium hydroxide is coated onto a separatesheet of paper in a suitable binder.

The coated sheet is immersed in the activator solution for a timesufficient to remove at least half of the lithium hydroxide bydissolving it into the activator solution.

Any of the common binders used in photographic products can be used,such as proteins, for example, gelatin, casein, zein, etc.; celluloseethers, e.g. methylcellulose, carboxymethylcellulose,hydroxyethylcellulose, etc.; water permeable polymeric materials, e.g.copoly ethylacrylate acryic acid, polyvinyl alcohol, etc. It will beunderstood that the binder is not critical provided it is of waterpermeable material. In a particularly useful embodiment of theinvention, a solution of lithium hydroxide in a binder is coated on apaper support in sufiicient amount to contain at least 0.5 gram persquare foot in the dried coating.

The following examples are intended to illustrate our invention but notto limit it in any way:

Example 1 A liquid activator having the following formula Potassiumcarbonate g./l 40.0 Ethylenediamine tetraacetic acid, sodium salt g./1p-Toluenesulfonic acid (monohydrate) g./l Potassium hydroxide, dilutesolution to neutralize acid, then to pH: 1 1.0.

was exhausted by using 200 matrices, making three copies per matrix.After every fifteen matrices, an 8 /2 inch by 11 inch sheet containingapproximately one gram lithium hydroxide per square foot was soaked for60 seconds, and the bath solution was maintained with the activatordiluted 2:1. Satisfactory copies were obtained.

Example 2 A liquid activator having the following components wasprepared:

This formula was exhausted by using to process 1000 matrices, making onecopy per matrix, with approximately 225 single copy colloid transfermatrices, letter size. The remainder were colloid transfer multiplecopy, letter size, and were used to make three copies per matrix, Afteran average of 16 matrices, 8 by 11 inch sheets containing approximatelyone gram lithium hydroxide per square foot were soaked in the activatorfor 60 seconds. The solution level was maintained with undiluted freshactivator. A total of 62 interleaving sheets and 7080 cc. (including the1800 cc. starting volume) of activator were employed in this example.

The quality of the copy obtained with the activation time range of toseconds was maintained throughout the testing period. The number oflegible multiple copies increased slightly and there was no sign ofimage bleeding, on either the single copy or multiple copy material.Maximum reflection density of the first copy was 0.81 in the freshactivator and 0.76 after 1000 sheets. The almost negligible drop inquality during the last several hundred sheets of the exhaustion testindicated that the composition of the bath reached equilibrium and copycould be made indefinitely. Each matrix sheet comprised a polyethylenecoated paper support having thereon an unhardened colloid silver halideemulsion containing a colloid hardening silver halide developer and anon-hardening silver halide developer.

Example 3 Anhydrous lithium hydroxide (450 grams) was dissolved in 4500cc. of solution which contained 5% methylcellulose in dimethylformamideand 70% ethylene chloride. This composition was coated on a polyethylenecoated support and the solvent evaporated to leave a coverage of about0.6 gram of lithium hydroxide per square foot as determined byconventional titration procedures. The coatings were used as describedin Example 1.

Example 4 To 1500 ml. of a 9.1% solution of the sodium salt of copoly(ethylacrylate-acrylic acid) at C., there was added 27.4 ml. of a 17%solution of the sodium salt of oleylmethyltaurine and 6.9 ml. of2-methyl-2,4-pentanediol. Next 137 grams of powdered anhydrous lithiumhydroxide Was added slowly with vigorous stirring. Stirring wascontinued until the lithium hydroxide was dissolved. Distilled water wasthen added to a total volume of 2000 ml.

Example 5 The activity of the liquid activator, similar to that ofExample 1, was maintained by aflixing a small amount of lithiumhydroxide to each matrix processed. Strips of lithium hydroxide coatingprepared according to Example 1 were cut to A inch by 8 /2 inches andattached to the reverse side of a colloid transfer matrix. The coatingcontained 0.68 gram of available lithium hydroxide per square foot. Onehundred of these modified matrices were processed normally in theactivator, making three copies per matrix. At the end of this test, thepH of the activator had dropped from 10.95 to 10.85 and copy quality andlatitude remained excellent. A similar test without the lithiumhydroxide strip on each matrix, showed the drop to be from 11.0 to10.35, at which point an acceptable copy was no longer available.

Example 6 Efforts were made to substitute other alkaline materials forlithium hydroxide. However, when sodium, potassium or ammonium hydroxidewere used, they were found to be unsuitable due to their hydroscopicnature. Weaker alkaline materials, such as sodium carbonate or sodiumphosphate, were also found to be unsuitable, since they'either failed tomaintain a sufficiently high pH or resulted in excessive salt content.

Lithium hydroxide can be suspended satisfactorily in gelatin or similarcolloid materials and coated on a suitable material to be used asinterleaving sheets, these sheets can be packaged with silver halideemulsions in proportions that closely compensate for the amount ofsilver halide developed. They form a convenient, automatic means ofactivator rejuvenation, since introduction of the sheets into the bathat appropriate intervals will maintain the proper pH throughout the lifeof the bath.

In an alternative method, the lithium hydroxide can be coated on eachmatrix sheet in an amount of at least about 0.001 gram per square footmatrix sheet, so that it acts to replenish the activator solution at thesame time that the exposed emulsion is being processed, In thisparticular embodiment, the coating could also be only on certain matrixsheets with the amount of lithium hydroxide coated in a larger amountper square foot. Preferably, the amount of lithium hydroxide added tothe activator should be at least enough to neutralize the amount of acidreleased by the silver halide emulsion. Since the frequency of additionand the nature of the activator may vary, the useful amount per squarefoot may vary from about 0.01 to 4.0 grams per square foot or about 0.02to 8.0 g./liter of activator solution. The pH may also vary dependingupon the activator.

The invention has been described in detail with particu lar reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1; A colloid transfer matrix comprising a support having thereon asubstantially unhardened silver halide emulsion containing a tanningtype silver halide developer and having on at least one side of thesupport, a coating containing at least about 0.01 gram per square footof lithium hydroxide.

2. A method of photographic reproduction comprising developing anexposed substantially non-hardened gelatino silver halide emulsion layeron a support, said emulsion being not harder than a gelatin layercontaining 0.7 gram of formaldehyde per pound of gelatin freshly coated,and containing a gelatin tanning silver halide developing agent and asubstantially non-tanning silver halide developing agent and having onthe reverse side of the support a coating containing at least 0.01 gramper square foot of lithium hydroxide, by activating the silver halideemulsion with an alkaline activating solution to obtain a hardenedgelatin and silver image in the areas of the emulsion layercorresponding to the highlights of the subject and substantiallyunhardened gelatin, silver and silver halide in the areas of theemulsion layer corresponding to the shadows of the subject, saiddeveloping being such as to prevent any substantial tanning of theemulsion layer in said areas corresponding to the shadows of thesubject, placing a sheet having an absorbent surface against saidemulsion layer while said emulsion layer is moist to cause only theshadow areas of the emulsion layer to transfer only a stratum of saidshadow areas of the emulsion layer to said sheet.

3. A method of photographic reproduction comprising developing anexposed substantially non-hardened gelatino silver halide emulsion layeron a support, said emulsion being not harder than a gelatin layercontaining 0.7 gram of formaldehyde per pound of gelatin freshly coated,and containing a gelatin tanning silver halide developing agent and asubstantially non-tanning silver halide developing agent and having onat least one side of the support a coating containing at leastsufiicient lithium hydroxide to add to the solution at least 0.02 to 8.0g./liter during the development period, by activating the silver halideemulsion with an alkaline activating solution to obtain a hardenedgelatin and silver image in the areas of the emul sion layercorresponding to the highlights of the subject and substantiallyunhardened gelatin, silver and silver halide in the areas of theemulsion layer corresponding to the shadows of the subject, saiddeveloping being such as to prevent any substantially tanning of theemulsion layer in said areas corresponding to the shadows of thesubject, placing a sheet having an absorbent surface against saidemulsion layer while said emulsion layer is moist to cause only theshadow areas of the emulsion layer to transfer only a stratum of saidshadow areas of the emulsion layer to said sheet.

4. A colloid transfer matrix as in claim 1 wherein said coating containsat least sufficient lithium hydroxide to neutralize the halogen acidformed by reducing the silver halide in the emulsion.

, References Cited UNITED STATES PATENTS McQueen 9666.4 Rodgers 96-3Fruchard et a1. 96-28 Yost 9628 Land 96--3 Willems et a1. 96-95 10NORMAN G. TORCHIN, Primary Examiner.

I. H, RAUBITSCHEK, R. FIGHTER,

Assistant Examiners.

2. A METHOD OF PHOTOGRAPHIC REPRODUCTION COMPRISING DEVELOPING ANEXPOSED SUBSTANTIALLY NON-HARDENED GELATINO SILVER HALIDE EMULSION LAYERON A SUPPORT, SAID EMULSION BEING NOT HARDER THAN A GELATIN LAYERCONTAINING 0.7 GRAM OF FORMALDEHYDE PER POUND OF GELATIN FRESHLY COATED,AND CONTAINING A GELATIN TANNING SILVER HALIDE DEVELOPING AGENT AND ASUBSTANTIALLY NON-TANNING SILVER HALIDE DEVELOPING AGENT AND HAVING ONTHE REVERSE SIDE OF THE SUPPORT A COATING CONTAINING AT LEAST 0.01 GRAMPER SQUARE FOOT OF LITHIUM HYDROXIDE, BY ACTIVATING THE SILVER HALIDEEMULSION WITH AN ALKALINE ACTIVATING SOLUTION TO OBTAIN A HARDENEDGELATIN AND SILVER IMAGE IN THE AREAS OF THE EMULSION LAYERCORRESPONDING TO THE HIGHLIGHTS OF THE SUBJECT AND SUBSTANTIALLYUNHARDENED GELATIN, SILVER AND SILVER HALIDE IN THE AREAS OF THEEMULSION LAYER CORRESPONDING TO THE SHADOWS OF THE SUBJECT, SAIDDEVELOPING BEING SUCH AS TO PREVENT ANY SUBSTANTIAL TANNING OF THEEMULSION LAYER IN SAID AREAS CORRESPONDING TO THE SHADOWS OF THESUBJECT, PLACING A SHEET HAVING AN ABSORBENT SURFACE AGAINST SAIDEMULSION LAYER WHILE SAID EMULSION LAYER IS MOIST TO CAUSE ONLY THESHADOW AREAS OF THE EMULSION LAYER TO TRANSFER ONLY A STRATUM OF SAIDSHADOW AREAS OF THE EMULSION LAYER TO SAID SHEET.